Transparent object with look front of all object

Hello Every one,

I am trying to create a surface with a bunch of point I have the script that slipts the surface into triangle. I want to that the surface look front all other object with transparency

For now, as you can see, objects behind look well, but objects front just disappear in pink color

I would like to look like this :

I am not really competent in graphic stuff.I try to solve with a shader. I create this shader base on my research

 Shader "Custom/Zone" {
     Properties {
         _Color ("Color", Color) = (1,1,1,0.5)
         _MainTex ("Color (RGB) Alpha (A)", 2D) = "white" {}
         //_Glossiness ("Smoothness", Range(0,1)) = 0.5
         //_Metallic ("Metallic", Range(0,1)) = 0.0
         // _Cutoff ("Base Alpha cutoff", Range (0,.9)) = .5
 
     }
      
     SubShader {
         Pass {
              Material {
                 Diffuse (1,1,1,1)
             }
              Cull Off
             ZTest Greater
             ZWrite On
          }
         Tags { "Queue"="Transparent" "RenderType"="Transparent" }
         LOD 200
         
         CGPROGRAM
         // Physically based Standard lighting model, and enable shadows on all light types
         #pragma surface surf Standard fullforwardshadows Lambert alpha
 
         // Use shader model 3.0 target, to get nicer looking lighting
         #pragma target 3.0
 
         sampler2D _MainTex;
 
         //#pragma surface surf 
 
 
 
         struct Input {
             float2 uv_MainTex;
         };
 
         half _Glossiness;
         half _Metallic;
         fixed4 _Color;
 
         void surf (Input IN, inout SurfaceOutputStandard o) {
             // Albedo comes from a texture tinted by color
             fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
             o.Albedo = c.rgb;
             o.Alpha = tex2D (_MainTex, IN.uv_MainTex).a;
             // Metallic and smoothness come from slider variables
             o.Metallic = _Metallic;
             o.Smoothness = _Glossiness;
             o.Alpha = c.a;
         }
         ENDCG
     }
     FallBack "Diffuse"
 }
 

Ps: for point and ligne i use UI image on world Space Canvas, I found here a shader that put it in front of every object. So if you have a solution to create my zone with UI element that can be great. :)